JP 2007-139739A (US 2007/0090831A) describes a rotation angle detection device to detect a rotation angle of various types of detection target. For example, as shown in FIG. 9, a rotation angle detection device 90 includes a cylindrical yoke 91, a pair of permanent magnets 92 and 93 as a magnetic field generation portion which rotates together with a detection target, Hall elements 94 and 95 as magnetism detection elements which rotate relative to the detection target, a support member 96 which fixes the Hall elements 94 and 95, and an engine control unit (ECU) 97 which executes a rotation angle detection program.
The Hall elements 94 and 95 are disposed to make an angle of 90° from each other in a rotational direction of the detection target. In response to a variation in the magnetic field caused by a rotation of the detection target, the Hall elements 94 and 95 output output signals 100 and 101, respectively. The output signals 100 and 101 are a sine-wave voltage and a cosine-wave voltage, respectively, which differ in phase by 90° from each other (see FIG. 10A). The ECU 97 detects a rotation angle 103 of the detection target on the basis of the output signals 100 and 101 (see FIG. 10B).
The sensitivity of the rotation angle detection device 90 is adjusted before shipment so that amplitudes of the output signals 100 and 101, respectively, from the Hall elements 94 and 95 as the magnetism detection elements are matched. In practice, however, as shown in FIG. 11A, an adjustment shift δ occurs in amplitude between the sine-wave output signal and the cosine-wave output signal due to irregularity in sensitivity adjustment or the like.
The ECU 97 detects the rotation angle 103 by performing an arc tangent computation by finding a ratio of the output signals 100 and 101. Hence, when an amplitude shift δ shown in FIG. 11A occurs between the sine-wave output signal and the cosine-wave output signal, an angular error (linearity error) is generated in a detected rotation angle as is shown in FIG. 11B.